Printing on plastic is a growing and challenging market for UV-curable inks and coatings. They have been successfully used for many years, but new opportunities arise daily that remind printers and formulators how difficult achieving adhesion can be.
This article gives a brief overview of four properties that are important to consider when printing on plastic. Surface tension is the most fundamental parameter to consider when printing on plastic. Most plastic films start out with a very low Surface tension and are typically treated to increase the Surface tension to 40 dynes/cm or higher. Substrate suppliers usually perform this treatment, but the effects will start to dissipate quickly.
In-line treatment is the best way for printers to ensure that the Surface tension is in the acceptable range at the time of printing. Corona discharge treatment (oxidative) is the most common treatment method. It can be used on numerous types of substrates without damaging heat-sensitive plastics. Gas flame treatment is used on more tolerant plastics.